The plasma membrane is composed of the phospholipid bilayer and cholesterol.The phospholipids have a head and two tails.The head is water loving, hence it is termed as polar/hydrophilic.The tails are nonpolar/ water fearing/hydrophobic.Both inside and outside the cell, water is vital thus the phospholipid line up in two layers where the head points outwards and the tails hidden in the middle.
